On gear change i heard a clucking noise

[alika]

on the bridges when My car is changing to lower gear automatically, i heard a clucking noise as if something got in the way. What could it be?

[tilakr]

is gear oil leaking?

[boynick]

nissan having problem like this is not common. but if the car is old then this may have happened. get the gear fixed.

[tilakr]

so ali what was the problem.